Hepatitis C virus (HCV) is a widespread, persistent disease affecting 1- 2% of the world's population. Only a fraction of HCV affected individuals respond to interferon therapy. Viral genotype has emerged as a clinically significant predictor for determining response to interferon. This proposal describes the application of a novel DNA fingerprinting technology, Cleavase Fragment Length Polymorphism (CFLP) to identifying HCV genotype. The specific aims of Phase II are to generate a two-pronged CFLP HCV genotyping kit for rapid identification of a broad range of HCV types and subtypes. This kit will be suitable for analysis of the highly conserved 5'NCR subgenomic region as a follow-on to widely used HCV detection systems as well as for analysis of the NS-5b region for high-resolution genotyping. Signature elements of CFLP cleavage patterns will be used to identify genotype in uncharacterized samples. The Phase II proposal includes internal validation testing and beta site testing in two prominent reference labs. The CFLP HCV genotyping kit will be capable of discriminating HCV genotype with up to 98% certainty (for single base changes, >98% for the multiple polymorphisms that form the basis of genotyping) in less time and for a lower cost than existing methods. PROPOSED COMMERCIAL APPLICATION Genotypic identification of hepatitis C Virus (HCV) is a rapidly growing area of research and clinical practice. In addition to affecting responsiveness to interferon, HCV genotype is likely to be an important factor in the evaluation of future antiviral therapies. CFLP is a fast, accurate, and user-friendly method for HCV genotyping. By developing a two-pronged assay, we propose to create a product suitable for immediate clinical use in detecting commonly occurring genotypes (based on the 5'NCR subgenomic region) as well as a more far-reaching method for higher-resolution typing (based on the NS-5b region).